The invention is directed to a method for the production of L-amino acids from .alpha.-ketocarboxylic acids by continuous fermentation with the aid of glutamate-producing bacteria in the presence of ammonium ions and of an energy supplier, especially glucose, with biomass retention.
L-amino acids can be obtained from .alpha.-keto acids by enzymatic conversion. Microbial conversion is also already known. Thus German OS 34 27 495 describes a method in which bacteria which excrete glutamate, especially bacteria of the genera Brevibacterium and Corynebacterium, are cultured in a culture medium within 6 to 40 hours, whereafter the .alpha.-ketocarboxylic acid to be transformed is added to the culture especially during the logarithmic growth phase (between approximately 20 and 72 hours) and is converted into L-amino acid.
According to another method described by the applicants (German patent application DE 34 19 585.8, the entire disclosure of which is hereby incorporated by reference), L-amino acids are likewise obtained by the microbial conversion of .alpha.-ketocarboxylic acids with the aid of glutamate-producing bacteria of the type named using growing or non-growing cells under aerobic conditions between 20.degree. and 45.degree. C. and a pH of 5-9 within 1-10 days. This method can be performed, as is indicated, continuously with retention of the biomass.
The microbial methods cited are relatively time consuming and the instant invention therefore has the task of improving the economy of the microbial conversion of .alpha.-keto acids into L-amino acids.